TP53 is mutated or deleted in over 50% of human cancers resulting in loss of p53-associated apoptosis, cell cycle arrest or DNA brake/repair response [11]; Loss of normal p53 function and resultant impaired G1 check point control correlates with increased resistance to both low- and high-dose ionizing radiation in several cancers including medulloblastoma [12-21]. This evidence concerns the gene TP53 and medulloblastoma.